Between 16 July 2011 and 5 September 2012, NASA’s space probe Dawn was orbiting Vesta, a protoplanet thought to have survived virtually intact since an early phase of Solar System formation. In this issue of Nature, two groups report on the encounter. Carle Pieters and co-workers find that space weathering on Vesta has followed a different course from that observed on the Moon and on Itokawa, the asteroid sampled in an Earth-return mission. On Vesta, weathering involved fine-scale regolith (soil) mixing that has removed clear traces of recent impact deposits. There are no signs of the nanophase metallic-particle deposits seen on the Moon and Itokawa. Thomas McCord and co-authors describe two main types of material on Vesta’s surface: bright and dark. The bright material may be uncontaminated indigenous Vesta basaltic soil, with the darker material derived from low-albedo impactors. Dawn has now moved on and is due to rendezvous with the protoplanet Ceres in February 2015.
AsteroidsDark and stormy weather (News & Views p45, doi: 10.1038/491045a)
- Distinctive space weathering on Vesta from regolith mixing processes (Letter p79, doi: 10.1038/nature11534)
- Dark material on Vesta from the infall of carbonaceous volatile-rich material (Letter p83, doi: 10.1038/nature11561)
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